The conventional seat belt restraint system includes a shoulder portion and a lap portion. One end of the shoulder portion is commonly attached to the frame of the vehicle at a location adjacent the occupant's shoulder. This is true, for example, with respect to buses and bus driver seats. By attaching the shoulder belt to the vehicle body, the vehicle body, rather than the vehicle seat, absorbs a relatively significant portion of the loads to which the occupant is exposed during a sudden deceleration of the vehicle.
The seats and seat belt assemblies must comply with the Federal Motor Vehicle Safety Standards (FMVSS). These standards have been developed to help minimize the possibility of the failure of seat and restraint designs by the forces acting on them as a result of a sudden deceleration or vehicle impact. For example, FMVSS 571.210 currently requires a seat and seat belt assembly for many vehicles to withstand forces in excess of 3,000 pounds applied to the shoulder belt and lap belt portions of the seat belt. Further, FMVSS 571.222 establishes occupant protection requirements for school bus passenger seating and restraining barriers, and SAE J2287 addresses design and performance standards for seats with integrated lap and shoulder restraints.
It would be desirable to attach the upper end of the shoulder belt to the frame of the seat, instead of to the frame of the vehicle. This position would render the shoulder belt more comfortable to the occupant and would facilitate the installation of the seat and the accompanying belts within a vehicle. The shoulder belt would not tend to chafe the neck of the occupant, as may arise when the seat belt is attached to the frame of the vehicle, due to such factors as the height of the occupant, the unevenness of the road, or whether the individual desires to recline in the seat. These considerations make wearing of a seat belt uncomfortable.
However, loading tests to which vehicle seats are commonly subjected require that a frame of the seat be much stronger when a shoulder belt is attached to the seat frame than is the case when the shoulder belt is attached to the vehicle body. Previous efforts to render the seat frame stronger have resulted in designs that are too bulky, heavy, or costly to be practical from a manufacturing standpoint. Further, previous efforts have focused on making the seat itself stronger, rather than the seat base assembly that supports the seat.
Thus, it is desirable to design a lightweight vehicle seating system, including seat base assembly, that allows a restraint assembly to be attached to the vehicle seating system itself.